A laminator is a kind of common office machines for laminating two films and an object, such as a photo or a business card, disposed between the two films. After the two films and the object disposed between the two films pass through a roller set inside the laminator, the object is sealed between the two films, so as to reduce the probability of the object being damaged and thus increase the storage life of the object. It should be noted that the films provided by different suppliers may have various thicknesses, and the thicker films need more heat energy for laminating during a heat laminating process. Therefore, with the film thicknesses increasing, the laminator needs to reduce a rotational speed of the roller set for increasing a time of the films receiving the heat energy, or increase a heating temperature of the roller set, and thus the films are capable of receiving more heat energy at the same time. In order to apply to the films with various thicknesses, a laminator with a rotational speed adjusting function or a heating temperature adjusting function becomes commercially available.
For example, the U.S. Pat. No. 7,556,077 discloses a laminator with a rotational speed adjusting function. Referring to FIG. 1A to FIG. 1C together, wherein FIG. 1A illustrates a side view of the laminator with changeable rotation speed of the U.S. Pat. No. 7,556,077 at a first rotational speed status, FIG. 1B illustrates a side view of the laminator with changeable rotation speed of the U.S. Pat. No. 7,556,077 at a second rotational speed status, and FIG. 1C illustrates a side view of the laminator with changeable rotation speed of the U.S. Pat. No. 7,556,077 at a third rotational speed status.
The laminator 1 comprises a driving device 11, a driving gear wheel set 12, a transmission gear set 13, a first roller 14, a second roller 15 and an adjusting device 16. Herein, the driving gear wheel set 12 comprises a first driving gear wheel 12a, a second driving gear wheel 12b, a third driving gear wheel 12c and a first shaft 12d. In addition, the transmission gear set 13 comprises a first transmission gear wheel 13a, a second transmission gear wheel 13b, a third transmission gear wheel 13c and a second shaft 13d. Furthermore, the first roller 14 comprises a first gear wheel 14a. Moreover, the second roller 15 comprises a second gear wheel 15a. Besides, the adjusting device 16 comprises a frame 16a and an adjusting rod 16b. 
Herein, the first shaft 12d connects with the driving device 11. Moreover, the first driving gear wheel 12a, the second driving gear wheel 12b and the third driving gear wheel 12c pass through the first shaft 12d respectively, wherein a diameter of the third driving gear wheel 12c is larger than a diameter of the first driving gear wheel 12a, and a diameter of the first driving gear wheel 12a is larger than a diameter of the second driving gear wheel 12b. Furthermore, the second shaft 13d is disposed over the first shaft 12d. In addition, the first transmission gear wheel 13a, the second transmission gear wheel 13b and the third transmission gear wheel 13c pass through the second shaft 13d respectively, wherein a diameter of the second transmission gear wheel 13b is larger than a diameter of the first transmission gear wheel 13a, and a diameter of the first transmission gear wheel 13a is larger than a diameter of the third transmission gear wheel 13c. Before the first transmission gear wheel 13a moves along the second shaft 13d to engage with the second transmission gear wheel 13b or the third transmission gear wheel 13c, neither the second transmission gear wheel 13b nor the third transmission gear wheel 13c is able to drive the second shaft 13d to rotate. Moreover, the first gear wheel 14a is disposed at an end of the first roller 14, and the end of the first roller 14 connects with the second shaft 13d. In addition, the second roller 15 is disposed over the first roller 14, the second gear wheel 15a is disposed at an end of the second roller 15, and the second gear wheel 15a engages with the first gear wheel 14a. Furthermore, the frame 16a surrounds the first transmission gear wheel 13a, while the adjusting rod 16b is located over the frame 16a for moving the frame 16a. 
An operating process of the laminator 1 is illustrated herein after. Referring to FIG. 1A first, before a user moves the adjusting rod 16b, the first transmission gear wheel 13a engages with the first driving gear wheel 12a. When the driving device 11 is activated, it brings the first shaft 12d and the first driving gear wheel 12a to rotate and thereby brings the first transmission gear wheel 13a and the second shaft 13d to rotate. Therefore, the first roller 14 and the first gear wheel 14a rotate with the second shaft 13d simultaneously. At the moment, the first gear wheel 14a rotates and thereby brings the second gear wheel 15a engaging with the first gear wheel 14a to rotate, and thus the first roller 14 and the second roller 15 simultaneously rotate with a first rotational speed. After that, the user is able to put two films with a first thickness and an object disposed between the two films inside the laminator, and thus the two films with the first thickness and the object disposed between the two films pass through the first roller 14 and the second roller 15, so as to seal the object between the two films with the first thickness.
When the user desires to seal the object between two films with a second thickness, and the second thickness is larger than the first thickness, the first roller 14 and the second roller 15 need to rotate with a lower rotational speed. Therefore, the user must to move the adjusting rod 16b leftward, and thus the frame 16a pushes the first transmission gear wheel 13a leftward to engage with the second transmission gear wheel 13b. At the time, the second transmission gear wheel 13b is unable to rotate relative to the second shaft 13d. After the driving device 11 is activated, the driving device 11 brings the first shaft 12d and the second driving gear wheel 12b to rotate and thereby brings the second transmission gear wheel 13b and the second shaft 13d to rotate, and thus the first roller 14 and the second roller 15 simultaneously rotate with a second rotational speed.
Since a diameter of the second driving gear wheel 12b is smaller than a diameter of the second transmission gear wheel 13b, and a diameter of the second driving gear wheel 12b is smaller than a diameter of the first driving gear wheel 12a, the required number of circles that the second driving gear wheel 12b rotates is more than that the first driving gear wheel 12a rotates in order to drive the second transmission gear wheel 13b to rotate one circle, and thus the second rotational speed is lower than the first rotational speed.
In contrast, when the user desires to seal the object between two films with a third thickness, and the third thickness is smaller than the first thickness, the first roller 14 and the second roller 15 need to rotate with a higher rotational speed. Thus, the user must to move the adjusting rod 16b rightward, and thus the frame 16a pushes the first transmission gear wheel 13a rightward to engage with the third transmission gear wheel 13c. At the time, the third transmission gear wheel 13c is unable to rotate relative to the second shaft 13d. After the driving device 11 is activated, the driving device 11 brings the first shaft 12d and the third driving gear wheel 12c to rotate and thereby brings the third transmission gear wheel 13c and the second shaft 13d to rotate, and thus the first roller 14 and the second roller 15 simultaneously rotate with a third rotational speed.
Since a diameter of the third driving gear wheel 12c is larger than a diameter of the third transmission gear wheel 13c, and a diameter of the third driving gear wheel 12c is larger than a diameter of the first driving gear wheel 12a, the number of circles that the third transmission gear wheel 13c being driven to rotate when the third driving gear wheel 12c rotates one circle is more than when the first driving gear wheel 12a rotates one circle, and thus the third rotational speed is higher than the first rotational speed.
According to a summary of the above mentioned descriptions, it is understood that the conventional laminator 1 provides a combination of the driving device 11, the driving gear wheel set 12, the transmission gear set 13, the first gear wheel 14a, the second gear wheel 15a and the adjusting device 16, and thus the first roller 14 and the second roller 15 can rotate with three different rotational speeds according to different film thicknesses.
It should be noted that the laminator disclosed in the above mentioned U.S. Pat. No. 7,556,077 has following disadvantages. The first disadvantage is that the user need to push the adjusting rod leftward or rightward for moving the first transmission gear wheel when the rotational speed of the first roller and the second roller is required to be adjusted. However, in a long term use, the adjusting rod is probably damaged or even fractured by the external force, and thus the conventional laminator is unable to adjust the rotational speed any more.
Besides, the laminator disclosed in the U.S. Pat. No. 7,556,077 does not have a function of adjusting heating temperature. Hence, no matter how the film thickness is, the heating device needs to heat the first roller and the second roller to the same heating temperature. Therefore, the laminator is in an environment with a high temperature for a long period during being operated, and thus a probability of melt damage is increased. In addition, when the thickness of the film required to be laminated is thinner, the user needs to wait for the same heating time as laminating a thicker film, and thus it is quite inconvenient to the user.
Accordingly, it is desired to provide an improved laminator for overcoming the disadvantages of the conventional laminator.